1. Field of the Invention
The present invention relates generally to a backlight unit and a display device using the same. More particularly, the present invention relates to an ultra-thin edge-type backlight unit allowing a local dimming driving and a scanning driving and using a low-cost light source, and a small display device of excellent screen quality.
2. Description of the Related Art
Flat display devices include Liquid Crystal Display (LCD), Plasma Display Panel (PDP), Organic Light Emitting Diode (OLED), Field Emission Display (FED), and so on. The PDP, the OLED, and the FED, which illuminates by itself, do not require a separate light source, whereas the LCD necessitates an external light source because it cannot illuminate by itself.
The LCD is widely used as a display device of mobile phones, handheld game consoles, Personal Digital Assistants (PDAs), monitors, and TVs. The Thin Film Transistor (TFT)-LED, which is the most common display module, cannot illuminate by itself and thus requires the use of a backlight. The TFT-LED functions as an optical shutter and represents pixel information using the backlight which supplies the uniform surface light from the rear.
Since the TFT-LCD uses the optical shutter in the front while illuminating the whole backlight, it has drawbacks compared to the Cathode Ray Tube (CRT), PDP, or the OLED that illuminate on a pixel basis by itself. The drawbacks include Contrast Ratio (C/R) decrease, energy consumption increase, and afterimages. To address those shortcomings, a local dimming technique which partially switches on and off the backlight, which was the uniform flat light source, is introduced.
However, the local dimming technique has been developed primarily in the backlight unit of the direct-type light source. That is, the local dimming using the partially flickering light source can be implemented only in the backlight including the direct-type light source. As for the direct-type backlight unit including a plurality of light sources in the back side of the panel, a housing of the light source is more complicated than that of an edge type and the uniform luminance requires a certain interval between the light source and the panel. Naturally, the direct-type backlight unit of the display device aiming at the miniature size and the ultra thickness is much thicker than the edge-type backlight unit.
Thus, what is needed is a backlight unit for reducing the thickness of the display device and realizing the local dimming technique.